Viewing points organized to watch transit of Venus

May 31 2012

Joe Carr will have his telescope ready to watch the rare event.

Skygazers have a rare opportunity next week to watch the dark circle of Venus cross the Sun - an astronomical event that will not happen again for 105 years.

"It's a golden opportunity to see a celestial event you won't be able to see again in your lifetime," said astronomy enthusiast Joe Carr.

Starting at 3: 05 p.m. Tuesday, Venus will appear to move across the Sun's shape for what is called the transit of Venus. The orbits of Mercury and Venus lie inside Earth's orbit, making them the only planets that can pass between the Earth and Sun to produce a transit.

On June 5, the Sun will set at 9: 49 p.m. in Victoria, midway through the phenomenon. Weather-permitting, there will be almost seven hours of transit-viewing time.

"Keep an eye on the western horizon wherever you plan on observing from," Carr said, adding that observers should try to make their way to higher ground.

Carr is a member of the Victoria Centre of the Royal Astronomical Society of Canada, which is inviting the public to watch the transit through telescopes set up around the city. There will be stations at the Royal B.C. Museum, Mount Tolmie, Cattle Point and outside Metchosin's municipal hall. Volunteer astronomers will provide guidance and telescopes will be fitted with filters to allow safe viewing.

The transit of Venus can be seen across the globe, with the best views from Australia, Japan, New Zealand and Eastern Russia.

"Where it's mostly visible is right dead centre in the Pacific," said Lauri Roche, president of the society's Victoria Centre.

The transit of Venus has only occurred seven times since the invention of the telescope and was first observed in 1639. The rare planetary alignment happens in a recurrent cycle, with a pair of Venus transits happening eight years apart. Between each pairing, there is an alternating 105-or 121-year gap, so although the last transit of Venus was in 2004, skygazers have to wait until 2117 for the next one.

The explorer Captain James Cook sailed from England to Tahiti to see the 1769 transit of Venus.

"I really get a rush of watching these things and putting myself back to 300 years ago," Roche said. The transit contributed to astronomical calculations of the solar system, specifically the size of planets, she said.

Venus is a similar size to Earth. During the transit, when Venus appears as a black dot crossing the Sun, observers can reflect on the Sun's size.

"The universe does seem fairly static, this gives you a sense of motion," Roche said.

It is possible to watch the natural phenomenon from home safely with a "pinhole camera." Make a small hole in a flat piece of cardboard and hold it to the sky, projecting the sunlight through the hole onto the ground. Then you can watch the projection on the ground. But remember - do not look directly at the Sun without the proper equipment. Sunglasses do not offer enough protection against retinal burns.